This application is related to and claims priority from Japanese Patent Applications No. Hei. 11-89792 filed on Mar. 30, 1999, and No. Hei. 11-242097 filed on Aug. 27, 1999, the contents of which are hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a double heat exchanger having plural heat-exchanging units. For example, the present invention is suitable for an integrated double heat exchanger in which a condenser for a refrigerant cycle and a radiator for cooling engine-cooling water of a vehicle are integrated.
2. Description of Related Art
In a conventional double heat exchanger described in JP-A-10-170184, radiator fins and condenser fins are integrated so that both radiator and condenser are integrated. Further, by adjusting louver states formed in the radiator fins and the condenser fins, heat-exchanging capacities of the radiator and the condenser are adjusted, respectively. The louvers are formed by cutting and standing a part of fin flat portions to disturb a flow of air passing through the fins. Here, the louver state means a louver standing angle, a louver cutting length, a louver width dimension and the number of louvers, for example.
However, in the conventional double heat exchanger, both heat-exchanging capacities of the radiator and the condenser are adjusted only by adjusting the louver states, while both core sizes of the radiator and condenser are set to be approximately equal. Therefore, in a vehicle where the heat-exchanging capacity necessary in the condenser is greatly smaller than the heat-exchanging capacity necessary in the radiator, it is difficult to adjust both the heat-exchanging capacities of the radiator and the condenser only using the louver states. That is, the size and performance of the condenser become larger than necessary conditions.
In view of the foregoing problems, it is an object of the present invention to provide a double heat exchanger in which heat-exchanging capacities of plural heat-exchanging units are adjusted while size and performance of a heat-exchanging unit are prevented from increasing more than necessary conditions.
According to the present invention, in a double heat exchanger including first and second heat-exchanging units, the first and second heat-exchanging units are disposed to be integrated through a side plate for reinforcing the first and second heat-exchanging units, and second tubes of the second heat-exchanging unit have a tube dimension in a tube longitudinal direction of the second tubes, smaller than that of first tubes of the first heat-exchanging unit. Therefore, it is possible to decrease heat-exchanging capacity of the second heat exchanger while size and weight of the second heat-exchanging unit are prevented from being increased more than necessary conditions. As a result, it prevents the size and weight of the double heat exchanger from being increased while heat-exchanging capacities of the first and second heat-exchanging units are adjusted.
Preferably, the second tubes have tube number smaller than that of the first tubes. Therefore, the size and the weight of the double heat exchanger further reduced while the heat-exchanging capacity of the second heat exchanger is prevented from being increased more than the necessary capacity. Further, the double heat exchanger includes a reinforcement plate disposed to extend from an end of the second core portion to the side plate, for supporting and fixing the second heat-exchanging unit. Therefore, the second heat-exchanging unit is tightly connected to the first heat-exchanging unit.
Preferably, the first heat-exchanging unit is disposed at a downstream air side from the second heat-exchanging unit linearly in an air-flowing direction, each of the first and second tubes is a flat-shaped tube having a major diameter dimension in the air-flowing direction and a minor diameter dimension in a direction perpendicular to both a tube longitudinal direction and the air-flowing direction, and each minor diameter dimension of the second tubes is smaller than each minor diameter dimension of the first tubes. Therefore, even when a temperature boundary layer generated at most upstream ends of the second tubes in the air-flowing direction is increased toward a downstream air side in the second core portion, it can prevent a distance (i.e., temperature boundary layer thickness) between the first tubes and the temperature boundary layer from being increased. As a result, the temperature boundary layer generated from the second heat-exchanging unit hardly deteriorates the heat-exchanging performance of the first heat-exchanging unit.
More preferably, both the first and second tubes have major diameter center lines corresponding to each other in the air-flowing direction. Therefore, air smoothly passes through the first and second heat-exchanging units in the air-flowing direction.
On the other hand, according to the present invention, each the first corrugated fin has a first fin height between adjacent first tubes, different from a second fin height of each second corrugated fin between adjacent second tubes. Further, the first tubes have a first pitch distance between adjacent first tubes at centers of the first tubes, the second tubes have a second pitch distance between adjacent second tubes at centers of the second tubes, the second pitch distance is equal to the first pitch distance, and a tube thickness of each first tube between adjacent first corrugated fins is different from a tube thickness of each the second tube between adjacent second corrugated fins. Therefore, at ends of the first core portion and the second core portion, where the side plate contacts, a difference between a core height of the first core portion and a core height of the second core portion is not greatly changed. Thus, the first and second core portions tightly contact the side plate without greatly increasing the kinds of the side plate.